1. Field of the Invention
The present invention relates to absorption chillers and more specifically to a system that conditions an absorption solution by removing from the solution certain contaminants, such as copper oxide.
2. Description of Related Art
Absorption chillers provide chilled water using a thermal-chemical process. Such a process typically involves cyclically vaporizing a refrigerant from an absorbent solution, expanding the refrigerant to create a cooling effect, and then reabsorbing the refrigerant back into the solution to perpetuate the cycle. Various refrigerant/absorbent solutions are known; however, water as the refrigerant and lithium bromide as the absorbent is one of the more common solutions.
Unfortunately, lithium bromide is a salt that under certain conditions can promote corrosion of iron and copper inside the chiller. In some cases, corrosion can weaken the hermetic integrity of the chiller, reduce heat transfer efficiencies, restrict solution flow, plug solution filters, interfere with pump operation, and obstruct movement of certain chiller components.
To avoid or minimize these problems, many chiller components are made of corrosion resistant materials. For example, heat exchanger tubes can be made of cupronickel, and the shell or other components can be made of various iron alloys, such as steel or even stainless steel where necessary.
Adding a chemical inhibitor to the solution can also reduce corrosion. Common inhibitors include lithium molybdates (e.g., lithium molybdate), nitrates (e.g., lithium nitrate), chromates (e.g., lithium chromate), and arsenite. However, even with corrosion resistant materials and rust inhibitors, some corrosion may still occur, especially when air leaks into the chiller.
Corrosion can create iron oxide and copper oxide that can become dispersed into the solution. The solution can be forced through a filter to remove the oxides; however, if the filters are not serviced regularly, the filter can become plugged with oxides. A buildup of oxides in the filter can reduce the filter""s porosity to a point where the inhibitors start becoming trapped in the filter. A filter that removes inhibitors from the solution can reduces a chiller""s ability to resist further corrosion.
It is an object of the present invention to remove copper oxide from an absorption solution by promoting a copper oxide plating process within a filter housing or within some other serviceable housing of an absorption chiller.
Another object is to feed the serviceable housing via a solution line that includes a flow restriction. The flow restriction allows the solution line to convey a relatively slow, continuous flow of solution from the chiller""s evaporator to help prevent the same solution from becoming too concentrated with lithium bromide.
Another object is to use a steady flow of solution from the chiller""s evaporator to help dissolve (on a generally continuous basis) a rust inhibitor from the chiller""s solution filter. The inhibitor may include, but is not limited to, molybdate, nitrate, arsenite, and chromate.
Yet, another object is to provide an absorption chiller with a sacrificial iron member that protects other components of the chiller during a copper oxide plating process.
A further object is to provide a filter for an absorption chiller with a plateable member upon which copper oxide may become plated.
One or more of these and other objects of the invention are provided by a filter system for an absorption chiller. To remove contaminants from the solution, the system includes a filter element disposed within a serviceable filter housing. A refrigerant or weak solution from the chiller""s evaporator and a stronger solution from the chiller""s absorber are conveyed to the filter housing on a generally continuous basis. The purpose is to avoid accumulating lithium bromide in the evaporator and to remove copper oxide from the solution by promoting a copper oxide plating process within the filter housing. The filter system is preferably provided with a plateable member and a sacrificial iron member.
The present invention provides a filter system for filtering contaminants from an absorption apparatus. The absorption apparatus circulates a solution whose concentration varies from being a weak solution at a first point, a stronger solution at a second point, and an intermediate solution at a third point. The filter system comprises a filter housing defining a filter inlet and a filter outlet; a first inlet line coupling the filter inlet to the first point to convey the weak solution to the filter housing; and a second inlet line coupling the filter inlet to the second point to convey the stronger solution to the filter housing, whereby the weak solution mixes with the stronger solution to produce the intermediate solution. The filter system also comprises a filter element disposed inside the filter housing, wherein the filter element has a porosity that is sufficiently fine to filter the contaminants from the intermediate solution upon the intermediate solution passing through the filter element. The filter system further comprises a discharge line connecting the filter outlet to the third point to convey the intermediate solution from the filter housing to the third point; and a flow restriction disposed in the first inlet line to ensure that solution flow through the first inlet line is less than solution flow through the second inlet line.
The present invention also provides an absorption apparatus that circulates a solution with a contaminant that includes copper oxide. The solution has a varying degree of concentration of lithium bromide in water. The absorption apparatus comprises a generator that vaporizes the water from the solution to produce a water vapor and a stronger solution; a condenser in fluid communication with the generator where the condenser condenses the water vapor to create a weak solution; an evaporator in fluid communication with the condenser where the evaporator receives the weak solution from the condenser and vaporizes the weak solution thereby recreating the water vapor; and an absorber in fluid communication with the evaporator and the generator. The absorber receives the water vapor from the evaporator, receives the stronger solution from the generator, and promotes the absorption of the water vapor into the stronger solution to create a first intermediate solution. The absorption apparatus also comprises a filter housing defining a filter inlet and a filter outlet; a first inlet line coupling the filter inlet to the evaporator such that the first inlet line conveys the weak solution from the evaporator to the filter inlet; and a second inlet line coupling the filter inlet to the absorber such that the second inlet line conveys the first intermediate solution from the absorber to the filter inlet. The weak solution mixes with the first intermediate solution to produce a second intermediate solution having a lower concentration than the first intermediate solution. The absorption apparatus further comprises a filter element disposed inside the filter housing wherein the filter element has a porosity that is sufficiently fine to filter the contaminant from the solution upon the second intermediate solution passing through the filter element; a discharge line coupling the filter outlet to the generator to convey the second intermediate solution from the filter housing eventually back to the generator; and a plateable member disposed inside the filter housing wherein the copper oxide becomes plated onto the plateable member.
The present invention further provides a method of conditioning a solution of an absorption apparatus. The absorption apparatus includes a generator, a condenser, an evaporator and an absorber, wherein the solution has a varying concentration of lithium bromide in water and includes a contaminant of copper oxide. The method comprises providing a plateable member within a housing; circulating the solution through the housing; plating the copper oxide on the plateable member; and using at least one valve to periodically isolate the housing from the generator, the condenser, the evaporator and the absorber to facilitate the servicing of the plateable member.
The present invention additionally provides apparatus for conditioning a solution of an absorption apparatus wherein the solution has a varying concentration of lithium bromide in water and includes a contaminant of copper oxide. The apparatus comprises a generator; a condenser; an evaporator; an absorber; a plateable member within a housing; a device circulating the solution through the housing; operable elements plating the copper oxide on the plateable member; and at least one valve to periodically isolate the housing from the generator, the condenser, the evaporator and the absorber to facilitate the servicing of the plateable member.